Night vision imaging is currently achieved by collecting and amplifying light. In one approach, ambient visible light (e.g., moonlight, starlight, plant luminescence and the like) is collected, converted to electrons, amplified and then converted to a visible image. In another approach, commonly referred to as thermal imaging, infrared photons emitted by an object that is warmer than the ambient environment (e.g., a living organism or a vehicle engine) are captured, such as with a charge-coupled device image sensor, and the image is then processed, amplified, and then displayed as a visible image.
A typical ambient light-collecting night vision device includes an objective lens that collects light that may not be readily visible with the naked eye, and focuses the collected light onto an image intensifier. The image intensifier includes a photocathode that absorbs the collected light and converts it to electrons. A microchannel plate is often used to further amplify the electronic signal. The amplified electronic signal is then drawn toward, and strikes, a phosphor screen, thereby causing the screen to emit visible light. Since the phosphor screen emits visible light in exactly the same pattern and contrast as collected by the objective lens, an image is created on the phosphor screen that closely corresponds to the scene observed by the objective lens. The green image formed on the phosphor screen has become characteristic of night vision devices.
Advances in night vision technology have brought about significant improvements in amplification. For example, so-called “Gen III” night vision devices have electron amplification ratios ranging from 30,000 to 50,000 and photon amplification ratios (i.e., photons out divided by photons in) of about 20 to 25. However, such night vision devices are relatively expensive and do not readily scale into large formats.
Accordingly, those skilled in the art continue with research and development efforts in the field of night vision.